Testing fixture for high voltage reliability of wafer-level semiconductor

Abstract

A testing fixture for high voltage reliability of a wafer-level semiconductor, relating to the technical field of semiconductor detection. The testing fixture for high voltage reliability of a wafer-level semiconductor of the present invention comprises a first insulating board, a first circuit board, and a second insulating board which are sequentially arranged; a target object is arranged between the first circuit board and the second insulating board; a probe base is further arranged on one side of the first circuit board, and a probe is mounted at the probe base; the first circuit board is connected to the target object by means of the probe, such that when a high-voltage electric signal is applied to the first circuit board, the high-voltage electric signal is transmitted to the target object by means of the probe to carry out high-voltage performance testing, and is isolated from the outside by means of the first insulating board and the second insulating board. The first insulating board and the second insulating board are arranged on two sides of the target object and first circuit board, thereby avoiding high-voltage sparking of the target object during high-voltage testing, guaranteeing testing safety while performing high-voltage testing on the target object.

Description

A wafer-level semiconductor high-voltage reliability test fixture Technical Field

[0001] The present invention relates to the field of semiconductor detection technology, and in particular to a wafer-level semiconductor high-voltage reliability test fixture. Background Art

[0002] High-voltage MOSFETs (MOSFETs) are increasingly being used as switching devices in new energy vehicles. Reliability verification of high-voltage MOSFETs can only be performed after wafers are cut and packaged into devices, which wastes significant manpower and resources. Currently, there is no method for performing high-voltage reliability verification of MOSFETs at the wafer level, necessitating a reliability verification device capable of performing both GB and RB reliability verification on MOSFETs at the wafer level. Commercially available WLR equipment only verifies GB, not high-voltage RB. However, high-voltage performance is a key characteristic of third-generation semiconductor ICs, making high-voltage RB reliability verification essential.

[0003] Summary of the Invention

[0004] An object of the first aspect of the present invention is to provide a wafer-level semiconductor high-voltage reliability test fixture to solve the problem in the prior art that the high-voltage performance of semiconductors cannot be verified.

[0005] Another object of the first aspect of the present invention is to solve the problem of scratches formed on the target by the probe.

[0006] In particular, the present invention provides a wafer-level semiconductor high-voltage reliability test fixture, comprising:

[0007] A first insulating plate, a first circuit board and a second insulating plate are arranged in sequence; a target object is arranged between the first circuit board and the second insulating plate; a probe holder is also provided on the side of the first circuit board facing the target object, and a probe is installed on the probe holder; the first circuit board is connected to the target object through the probe so that when a high-voltage electrical signal is applied at the first circuit board, the high-voltage electrical signal is transmitted to the target object through the probe to perform a high-voltage performance test, and the high-voltage electrical signal is isolated from the outside world by the first insulating plate and the second insulating plate. The probe is also configured to transmit the test electrical signal to the target object and transmit a feedback signal to the first circuit board when the test electrical signal is applied at the first circuit board.

[0008] Optionally, the first insulating plate and the second insulating plate are both selected from one of a plastic plate and a ceramic plate.

[0009] Optionally, the size of the plastic plate is 10-20 mm.

[0010] Optionally, it also includes:

[0011] a first heating plate, the first heating plate being arranged on a side of the second insulating plate away from the target object;

[0012] a second circuit board for transmitting a heating electrical signal to the first heating plate; the second circuit board is arranged on a side of the first insulating plate away from the first circuit board; and

[0013] An insulating block is arranged at the position of the target object, and the insulating block is provided with a plurality of first through holes, and conductive pillars are arranged in the first through holes. A second through hole for the conductive pillars to pass through is provided at the second insulating plate, so that one end of the conductive pillar is connected to the probe, and the other end passes through the first through hole and the second through hole and is connected to the first heating plate. The heating electrical signal passes through the first insulating plate, the first circuit board, the probe and the conductive pillar, and then is transmitted to the first heating plate.

[0014] Optionally, a second heating plate is further included, which is arranged on the side of the first circuit board opposite to the probe seat, and its shape is adapted to the probe seat. The second heating plate is electrically connected to the second circuit board so that the heating electrical signal of the second circuit board is transmitted to the first heating plate and the second heating plate at the same time, thereby causing the second heating plate to be heated at the same time as the first heating plate.

[0015] Optionally, a heat sink is further included, on which the target object is arranged, and the heat sink is arranged between the target object and the first heating plate. The probe is also connected to the heat sink to transmit the high-voltage electrical signal to the heat sink and then to the target object. At the same time, the heat at the first heating plate is transferred to the target object through the heat sink.

[0016] Optionally, the heat sink comprises:

[0017] at least one vacuum hole, disposed near a side of the target object, the vacuum hole being used to hold the target object in close contact with the heat sink; and

[0018] The groove has an opening arranged at the periphery of the heat sink and is used for arranging the insulating block.

[0019] Optionally,

[0020] The invention further comprises a heat preservation plate, wherein the heat preservation plate is arranged on a side of the first heating plate away from the second insulating plate.

[0021] Optionally, a sealing assembly is further included, the sealing assembly comprising:

[0022] a sealing frame, forming a frame-shaped structure with an opening, wherein the opening is connected to a side of the first circuit board where the probe seat is provided to form a sealed cavity, wherein the sealed cavity is used to accommodate the probe seat, the target object, the heat sink, the first heating plate, the second insulating plate, and the insulation plate; and

[0023] A sealing ring is provided at an opening of the sealing frame to seal a connection between the sealing frame and the first circuit board.

[0024] Optionally, a metal decorative plate is further included, which is arranged on a side of the first insulating plate away from the first circuit board. A third through hole is provided on the metal decorative plate, and the second circuit board is arranged at the position of the third through hole.

[0025] In this solution, a probe holder is arranged between the target object and the first circuit board. A probe is arranged at the probe holder, which can transmit the high-voltage electrical signal at the first circuit board to the target object to perform a high-voltage test on the target object. A first insulating plate and a second insulating plate are arranged on both sides of the target object and the first circuit board. The first insulating plate and the second insulating plate prevent high-voltage sparks from the target object during the high-voltage test, thereby ensuring the safety of the test while performing a high-voltage test on the target object.

[0026] In this embodiment, the second heating plate and the first heating plate are respectively arranged on the two sides of the probe base and the target object. While the first heating plate heats the target object, the second heating plate will also heat up. This can effectively avoid scratches on the target object caused by the different heating rates on both sides of the probe.

[0027] This solution utilizes a sealed space between the sealing assembly and the cover plate to prevent oxidation from outside air during heating, while also providing high-voltage isolation. Furthermore, the sealing assembly ensures a pressure of 0.6 mPa within the sealed cavity, allowing for the introduction of high-pressure arc-extinguishing gas to further prevent high-voltage ignition.

[0028] Based on the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will become more aware of the above and other objects, advantages and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings:

[0030] FIG1 is a schematic structural diagram of a wafer-level semiconductor high-voltage reliability test fixture according to one embodiment of the present invention;

[0031] FIG2 is a schematic exploded view of a wafer-level semiconductor high-voltage reliability test fixture according to one embodiment of the present invention;

[0032] FIG3 is a schematic structural diagram of a cover plate according to one embodiment of the present invention;

[0033] FIG4 is a schematic structural diagram of the back side of a cover plate according to one embodiment of the present invention;

[0034] FIG5 is a schematic structural diagram of the back side of a cover plate according to another embodiment of the present invention;

[0035] FIG6 is a schematic structural diagram of a second circuit board according to an embodiment of the present invention;

[0036] FIG7 is a schematic structural diagram of a heat sink according to an embodiment of the present invention;

[0037] FIG8 is a schematic structural diagram of a sealing assembly according to one embodiment of the present invention;

[0038] FIG9 is a schematic exploded view of a sealing assembly according to one embodiment of the present invention;

[0039] FIG10 is a schematic structural diagram of a sealing assembly according to another embodiment of the present invention;

[0040] FIG. 11 is a partially enlarged schematic cross-sectional view of a sealing assembly according to one embodiment of the present invention. DETAILED DESCRIPTION

[0041] As a specific embodiment of the present invention, the wafer-level semiconductor high-voltage reliability test fixture 100 of this embodiment is used to perform reliability testing on wafer-level semiconductors, especially GB (Gate bias) and RB (reverse bias) of high-voltage Mosfet. Among them, the reverse bias test needs to be tested under high voltage. As shown in Figures 1 and 2, the semiconductor high-voltage reliability test fixture 100 of this embodiment may include a first insulating plate 10, a first circuit board 20, and a second insulating plate 30 arranged in sequence. A target object 40 is arranged between the first circuit board 20 and the second insulating plate 30. A probe holder 50 is also provided on the side of the first circuit board 20 facing the target object 40, and a probe is installed at the probe holder 50. The first circuit board 20 is connected to the target object 40 through a probe so that when a high-voltage electrical signal is applied at the first circuit board 20, the high-voltage electrical signal is transmitted to the target object 40 through the probe for high-voltage performance testing, and the high-voltage electrical signal is isolated from the outside world by the first insulating plate 10 and the second insulating plate 30. The probe is also configured to transmit the test electrical signal to the target object 40 and transmit a feedback signal to the first circuit board 20 when the test electrical signal is applied at the first circuit board 20.

[0042] Specifically, in this embodiment, a probe holder 50 is arranged between the target object 40 and the first circuit board 20. A probe is arranged at the probe holder 50, which can transmit the high-voltage electrical signal at the first circuit board 20 to the target object 40 to perform a high-voltage test on the target object 40. A first insulating plate 10 and a second insulating plate 30 are arranged on both sides of the target object 40 and the first circuit board 20. The first insulating plate 10 and the second insulating plate 30 prevent the high voltage of the target object 40 from sparking during the high-voltage test, thereby ensuring the safety of the test while performing a high-voltage test on the target object 40.

[0043] Specifically, the target 40 of this embodiment is generally a wafer-level semiconductor chip, typically a SiC wafer, which can be 4 inches or 6 inches in size. In addition, the high voltage of this embodiment can range from tens of volts to 3000 volts, thereby ensuring high-voltage reliability testing of the wafer.

[0044] As a specific embodiment of the present invention, the first insulating plate 10 and the second insulating plate 30 of this embodiment can be selected from either a plastic plate or a ceramic plate. Ceramics, as a high-performance insulating material, can effectively prevent high-voltage sparks. Although plastic plates are also insulating materials, if they are relatively thin, they can easily be broken down by high voltage and cause sparks when the voltage is high. Therefore, to ensure that sparks can still be prevented at a voltage of 3000 volts, this embodiment requires the plastic plate to be 10-20 mm thick. For example, it can be 10 mm, 15 mm, or 20 mm. The minimum thickness cannot be less than 10 mm.

[0045] As a specific embodiment of the present invention, when the first insulating plate 10 or the second insulating plate 30 of this embodiment is a plastic plate or a ceramic plate, it can prevent high voltage sparks when high voltage is applied to the test fixture of the present application.

[0046] As a specific embodiment of the present invention, the semiconductor high-voltage reliability test fixture 100 of this embodiment may further include a first heating plate 60, a second circuit board 70, and an insulating block 61 positioned at the target object 40. The first heating plate 60 is positioned on the side of the second insulating plate 30 away from the target object 40. The second circuit board 70 is used to transmit a heating electrical signal to the first heating plate 60. The second circuit board 70 is positioned on the side of the first insulating plate 10 away from the first circuit board 20. The insulating block 61 positioned at the target object 40 is provided with a plurality of first through-holes 611, each of which contains a conductive post 612. The second insulating plate 30 is provided with a second through-hole 31 for the conductive post 612 to pass through. This allows one end of the conductive post 612 to connect to a probe, while the other end passes through the first through-hole 611 and the second through-hole 31 and then connects to the first heating plate 60. The heating electrical signal passes through the first insulating plate 10, the first circuit board 20, the probe, and the conductive post 612, and finally to the first heating plate 60.

[0047] In this embodiment, the heating electrical signal is transmitted to the first heating plate 60 via the second circuit board 70 to heat the target 40, thereby allowing the target 40 to be heated during high-voltage performance testing. Specifically, in this embodiment, the target 40 can be heated to approximately 175 degrees Celsius while undergoing high-voltage testing, allowing the performance of the target 40 to be tested within a temperature range at or below this temperature.

[0048] As a specific embodiment of the present invention, the semiconductor high-voltage reliability test fixture 100 of this embodiment may also include a second heating plate 80, which is arranged on the side of the first circuit board 20 opposite to the probe seat 50, and its shape is adapted to the probe seat 50. The second heating plate 80 is electrically connected to the second circuit board 70 so that the heating electrical signal of the second circuit board 70 is transmitted to the first heating plate 60 and the second heating plate 80 at the same time, thereby causing the second heating plate 80 and the first heating plate 60 to be heated at the same time.

[0049] Specifically, the second heating plate 80 and the first heating plate 60 in this embodiment are respectively arranged on the two side surfaces of the probe base 50 and the target object 40. While the first heating plate 60 heats the target object 40, the second heating plate 80 is also heated. This can effectively avoid scratches on the target object 40 caused by the different heating rates on both sides of the probe.

[0050] As a specific embodiment of the present invention, as shown in Figures 3 to 5, this embodiment may further include a metal decorative plate 90 above the target object 40. The metal decorative plate 90 is arranged on the side of the first insulating plate 10 away from the first circuit board 20. A third through hole 91 is provided at the metal decorative plate 90, and the second circuit board 70 is provided at the position of the third through hole 91.

[0051] Specifically, as shown in FIG6 , a plurality of probe solder joints are provided on the second circuit board 70 , which may include a first solder joint 71 for high voltage power input, a second solder joint 72 for detecting temperature, and a third solder joint 73 for inputting heating electrical signals.

[0052] Specifically, the first insulating plate 10 of this embodiment is arranged between the second circuit board 70 and the first circuit board 20, and the first insulating plate 10 is provided with a probe mounting hole corresponding to the solder point on the second circuit board 70. When in use, a probe is set at this position, and the probe can be used to connect the electrical signals at the second circuit board 70 and the first circuit board 20.

[0053] Specifically, in addition to solder points on the first circuit board 20 corresponding to solder points on the second circuit board 70 to direct electrical signals from the second circuit board 70 to the target object 40, first heating plate 60, and second heating plate 80 below, the second circuit board 70 is also provided with a plurality of solder points for flowing a small current for detecting various properties of the target object 40, as well as external power supply solder points for obtaining electrical signals fed back from the target object 40, first heating plate 60, and second heating plate 80. That is, in this embodiment, after the high-voltage electrical signal, heating electrical signal, and test electrical signal are input through the first circuit board 20 and the second circuit board 70, feedback signals can be obtained at the corresponding solder point positions on the first circuit board 20 by an external detection device, thereby obtaining various electrical signals of the target object 40.

[0054] Specifically, in this embodiment, the metal decorative plate 90, the first insulating plate 10 and the first circuit board 20 form a three-layer square plate structure, the second heating plate 80 is fixed on the first circuit board 20 and is located between the first insulating plate 10 and the first circuit board 20, and the probe seat 50 is also fixed on the first circuit board 20 and is located on the side of the first circuit board 20 away from the first heating plate 60.

[0055] Specifically, as shown in Figures 3 to 5, the first circuit board 20, the first insulating plate 10 and the metal decorative plate 90 are fastened to each other to form a cover plate as a whole 101. Two metal strips 102 are provided on two opposite sides of the cover plate as a whole 101. The metal strips 102 can be used to resist wear when inserted into a drawer. A handle 103 is provided on the other side of the cover plate as a whole 101 for easy carrying. A magnetic metal part 104 is provided on the side of the cover plate as a whole 101 opposite to the handle 103. The magnetic metal part 104 is used to attract the magnet in the drawer after the clamp is inserted into the drawer. A metal part 105 is also provided on the same side of the cover plate as the magnetic metal part 104. The metal part 105 is used for the metal sensing device in the drawer to detect the switch when it approaches, thereby determining whether the clamp has been placed properly.

[0056] As a specific embodiment of the present invention, as shown in FIG7 , the wafer-level semiconductor high-voltage reliability test fixture 100 of this embodiment may further include a heat sink 110. Specifically, a target 40 is disposed on the heat sink 110, and the heat sink 110 is disposed between the target 40 and the first heating plate 60. A probe is further connected to the heat sink 110 to transmit a high-voltage electrical signal to the heat sink 110 and then to the target 40. Simultaneously, heat from the first heating plate 60 is transferred to the target 40 via the heat sink 110.

[0057] Specifically, in this embodiment, the target object 40 is set on the heat sink 110. When the first heating plate 60 is heated, the heat first reaches the heat sink 110 and is then transferred to the target object 40 by the heat sink 110, so that the target object 40 is heated more evenly.

[0058] Specifically, the heat sink 110 is a circular structure with a step 111 formed in the middle for placing the target 40. The heat sink 110 can be made of copper or copper plated with gold.

[0059] As a specific embodiment of the present invention, the test fixture of this embodiment may further include a heat preservation plate 120 . The heat preservation plate 120 is disposed on a side of the first heating plate 60 away from the second insulating plate 30 .

[0060] Specifically, the target 40, heat sink 110, second insulating plate 30, first heating plate 60, and thermal insulation plate 120 are sequentially arranged below the cover plate 101. The heat sink 110, second insulating plate 30, first heating plate 60, and thermal insulation plate 120 are substantially the same size and are all circular. The thermal insulation plate 120 can be made of silicone.

[0061] As a specific embodiment of the present invention, the heat sink 110 of this embodiment may include at least one vacuum hole 112 and a groove 113. Specifically, the vacuum hole 112 is located on a side near the target object 40 and is used to hold the target object 40 in close contact with the heat sink 110. The vacuum hole can be used to evacuate the target object 40 using external vacuum equipment, thereby placing the target object 40 in close contact with the heat sink 110. The groove 113 is located at the periphery of the heat sink 110 and is used to accommodate the insulating block 61.

[0062] As a specific embodiment of the present invention, as shown in Figures 8 to 10, the wafer-level semiconductor high-voltage reliability test fixture 100 of this embodiment may also include a sealing component 130, and the sealing component 130 may include a sealing frame 131 and a sealing ring 132. The sealing frame 131 forms a frame-type structure with an opening, and the opening is connected to the side of the first circuit board 20 where the probe seat 50 is provided to form a sealed cavity, which is used to accommodate the probe seat 50, the target object 40, the heat sink 110, the first heating plate 60, the second insulating plate 30, and the insulation plate 120. The sealing ring 132 is provided at the opening position of the sealing frame 131 to seal the connection when the sealing frame 131 is connected to the first circuit board 20.

[0063] Specifically, as shown in Figure 11, a sealing ring groove 133 is provided at the opening of the sealing frame 131. The sealing ring groove 133 is dovetail-shaped, and the sealing ring 132 is inserted into the sealing ring groove 133 to connect with the sealing frame 131. After the sealing ring 132 is installed in the groove, it does not need to be glued or fixed in other ways, and is locked in place by the structure. Specifically, the depth of the sealing ring groove 133 is less than the diameter of the sealing ring 132, so that when the sealing ring 132 is installed in the sealing ring groove 133, the sealing ring 132 is partially exposed. Therefore, when the sealing frame 131 is connected to the cover plate 101, the sealing ring 132 is used to abut and seal.

[0064] Specifically, the bottom of the sealing frame 131 is provided with threaded seat mounting holes 134, positioning holes 135, vacuum suction holes 136, and screw holes 137. The threaded seat mounting holes 134 accommodate threaded seats 138, each of which has three screw holes. The threaded seat mounting holes 134 are not fully threaded; instead, they include a light hole that is larger than the threaded section and serves to guide the threaded seats 138. The positioning holes 135 are used to position the sealing frame 131, and the vacuum suction holes 136 are used to position the wafer (target object 40). The screw holes 137 are used to mount the heat sink 110.

[0065] Specifically, in this embodiment, a sealed space is formed between the sealing assembly 130 and the cover plate 101, thereby preventing oxidation from external air during heating of the target 40 and achieving high-voltage isolation. Furthermore, the sealing assembly 130 ensures that the pressure within the sealed cavity reaches 0.6 mPa, allowing for the introduction of high-pressure arc-extinguishing gas to further prevent high-voltage ignition.

[0066] At this point, those skilled in the art will recognize that, although a number of exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications consistent with the principles of the present invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and deemed to cover all such other variations or modifications.

Claims

1. A wafer-level semiconductor high-voltage reliability test fixture, wherein: The wafer-level semiconductor high-voltage reliability test fixture includes: A first insulating plate, a first circuit board and a second insulating plate are arranged in sequence; a target object is arranged between the first circuit board and the second insulating plate; a probe seat is also arranged on the side of the first circuit board facing the target object, and a probe is installed on the probe seat; the first circuit board is connected to the target object through the probe so that when a high-voltage electrical signal is applied at the first circuit board, the high-voltage electrical signal is transmitted to the target object through the probe to perform a high-voltage performance test, and the high-voltage electrical signal is isolated from the outside world by the first insulating plate and the second insulating plate, and the probe is also configured to transmit the test electrical signal to the target object and transmit a feedback signal to the first circuit board when the test electrical signal is applied at the first circuit board.

2. The wafer-level semiconductor high-voltage reliability test fixture according to claim 1, wherein: The first insulating plate and the second insulating plate are both selected from one of a plastic plate and a ceramic plate.

3. The wafer-level semiconductor high-voltage reliability test fixture according to claim 2, wherein: The size of the plastic plate is 10-20 mm.

4. The wafer-level semiconductor high-voltage reliability test fixture according to any one of claims 1 to 3, further comprising: a first heating plate, the first heating plate being arranged on a side of the second insulating plate away from the target object; a second circuit board, which is used to transmit a heating electrical signal to the first heating plate; the second circuit board is arranged on a side of the first insulating plate away from the first circuit board; and An insulating block is arranged at the position of the target object, the insulating block is provided with a plurality of first through holes, a conductive column is arranged in the first through hole, and a second through hole for the conductive column to pass through is arranged at the second insulating plate, so that one end of the conductive column is connected to the probe, and the other end passes through the first through hole and the second through hole and is connected to the first heating plate, and the heating electrical signal passes through the first insulating plate, the first circuit board, the probe and the conductive column, and then is transmitted to the first heating plate piece.

5. The wafer-level semiconductor high-voltage reliability test fixture according to claim 4 further includes a second heating plate, which is arranged on the side of the first circuit board opposite to the probe seat, and its shape is adapted to the probe seat, and the second heating plate is electrically connected to the second circuit board so that the heating electrical signal of the second circuit board is transmitted to the first heating plate and the second heating plate at the same time, thereby allowing the second heating plate to be heated simultaneously with the first heating plate.

6. The wafer-level semiconductor high-voltage reliability test fixture according to claim 4 further includes a heat sink, on which the target object is set, and the heat sink is set between the target object and the first heating plate, and the probe is also connected to the heat sink to transmit the high-voltage electrical signal to the heat sink and then to the target object, and at the same time, the heat at the first heating plate is transferred to the target object through the heat sink.

7. The wafer-level semiconductor high-voltage reliability test fixture according to claim 6, wherein: The heat sink comprises: at least one vacuum hole, disposed near a side of the target object, the vacuum hole being used to place the target object in close contact with the heat sink; and The groove, whose opening is arranged at the periphery of the heat sink, is used to arrange the insulating block. 8 . The wafer-level semiconductor high-voltage reliability test fixture according to claim 6 , further comprising a heat preservation plate, wherein the heat preservation plate is disposed at a side of the first heating plate away from the second insulating plate.

9. The wafer-level semiconductor high-voltage reliability test fixture according to claim 8, further comprising a sealing component, wherein the sealing component comprises: A sealing frame, forming a frame structure with an opening, wherein the opening is connected to a side of the first circuit board where the probe seat is provided to form a sealed cavity, wherein the sealed cavity is used to accommodate the probe seat, the target object, the heat sink, the first heating plate, the second insulating plate, and the heat preservation plate; and A sealing ring is arranged at the opening of the sealing frame to seal the connection when the sealing frame is connected to the first circuit board.

10. The wafer-level semiconductor high-voltage reliability test fixture according to claim 4 further includes a metal decorative plate, which is arranged on the side of the first insulating plate away from the first circuit board, a third through hole is arranged at the metal decorative plate, and the second circuit board is arranged at the position of the third through hole.

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